Re: [Xen-devel] [PATCH 3/3] tools: sched: add support for 'null' scheduler

[Dario Faggioli <dario.faggioli@xxxxxxxxxx>]

On Fri, 2017-04-07 at 10:42 +0100, Wei Liu wrote:
> On Thu, Apr 06, 2017 at 05:18:33PM +0200, Dario Faggioli wrote:
> > 
> > Wei acked this patch in v1 (20170321170902.ndk6h5ylyfkk4coo@citrix.
> > com)
> > but that was before you raised this, so I'm happy to resend with
> > this
> > changed, and doing whatever he prefers with his ack.
> > 
> > Wei?
> 
> I don't feel strongly about this. But if you want to return success
> in
> the get function, please make sure you initialise output to a known
> state, instead of returning random garbage.
> 
Sure. That should not be a problem, as libxl_domain_sched_params_get()
calls, as the first thing it does, libxl_domain_sched_params_init(),
which sets all scinfo fields to their default.

Whatever I return, I won't touch scinfo at all, which means I'm just
returning those defaults.

So, can the below patch --which would make George much happier :-D
--also have your Ack?

Thanks and Regards,
Dario
---
tools: sched: add support for 'null' scheduler

From: Dario Faggioli <dario.faggioli@xxxxxxxxxx>

It being very very basic, also means this scheduler does
not need much support at the tools level (for now).

Basically, just the definition of the symbol of the
scheduler itself and a couple of stubs.

Signed-off-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx>
---
 tools/libxl/libxl.h         |    6 ++++++
 tools/libxl/libxl_sched.c   |   24 ++++++++++++++++++++++++
 tools/libxl/libxl_types.idl |    1 +
 3 files changed, 31 insertions(+)

diff --git a/tools/libxl/libxl.h b/tools/libxl/libxl.h
index a402236..cf8687a 100644
--- a/tools/libxl/libxl.h
+++ b/tools/libxl/libxl.h
@@ -210,6 +210,12 @@
 #define LIBXL_HAVE_SCHED_RTDS 1
 
 /*
+ * LIBXL_HAVE_SCHED_NULL indicates that the 'null' static scheduler
+ * is available.
+ */
+#define LIBXL_HAVE_SCHED_NULL 1
+
+/*
  * libxl_domain_build_info has u.hvm.viridian_enable and _disable bitmaps
  * of the specified width.
  */
diff --git a/tools/libxl/libxl_sched.c b/tools/libxl/libxl_sched.c
index 84d3837..d763b9a 100644
--- a/tools/libxl/libxl_sched.c
+++ b/tools/libxl/libxl_sched.c
@@ -178,6 +178,20 @@ static int sched_arinc653_domain_set(libxl__gc *gc, 
uint32_t domid,
     return 0;
 }
 
+static int sched_null_domain_set(libxl__gc *gc, uint32_t domid,
+                                 const libxl_domain_sched_params *scinfo)
+{
+    /* There aren't any domain-specific parameters to be set. */
+    return 0;
+}
+
+static int sched_null_domain_get(libxl__gc *gc, uint32_t domid,
+                               libxl_domain_sched_params *scinfo)
+{
+    /* There aren't any domain-specific parameters to return. */
+    return 0;
+}
+
 static int sched_credit_domain_get(libxl__gc *gc, uint32_t domid,
                                    libxl_domain_sched_params *scinfo)
 {
@@ -730,6 +744,9 @@ int libxl_domain_sched_params_set(libxl_ctx *ctx, uint32_t 
domid,
     case LIBXL_SCHEDULER_RTDS:
         ret=sched_rtds_domain_set(gc, domid, scinfo);
         break;
+    case LIBXL_SCHEDULER_NULL:
+        ret=sched_null_domain_set(gc, domid, scinfo);
+        break;
     default:
         LOGD(ERROR, domid, "Unknown scheduler");
         ret=ERROR_INVAL;
@@ -758,6 +775,7 @@ int libxl_vcpu_sched_params_set(libxl_ctx *ctx, uint32_t 
domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter setting not supported for this 
scheduler");
         rc = ERROR_INVAL;
         break;
@@ -792,6 +810,7 @@ int libxl_vcpu_sched_params_set_all(libxl_ctx *ctx, 
uint32_t domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter setting not supported for this 
scheduler");
         rc = ERROR_INVAL;
         break;
@@ -832,6 +851,9 @@ int libxl_domain_sched_params_get(libxl_ctx *ctx, uint32_t 
domid,
     case LIBXL_SCHEDULER_RTDS:
         ret=sched_rtds_domain_get(gc, domid, scinfo);
         break;
+    case LIBXL_SCHEDULER_NULL:
+        ret=sched_null_domain_get(gc, domid, scinfo);
+        break;
     default:
         LOGD(ERROR, domid, "Unknown scheduler");
         ret=ERROR_INVAL;
@@ -858,6 +880,7 @@ int libxl_vcpu_sched_params_get(libxl_ctx *ctx, uint32_t 
domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter getting not supported for this 
scheduler");
         rc = ERROR_INVAL;
         break;
@@ -890,6 +913,7 @@ int libxl_vcpu_sched_params_get_all(libxl_ctx *ctx, 
uint32_t domid,
     case LIBXL_SCHEDULER_CREDIT:
     case LIBXL_SCHEDULER_CREDIT2:
     case LIBXL_SCHEDULER_ARINC653:
+    case LIBXL_SCHEDULER_NULL:
         LOGD(ERROR, domid, "per-VCPU parameter getting not supported for this 
scheduler");
         rc = ERROR_INVAL;
         break;
diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
index d970284..d42f6a1 100644
--- a/tools/libxl/libxl_types.idl
+++ b/tools/libxl/libxl_types.idl
@@ -191,6 +191,7 @@ libxl_scheduler = Enumeration("scheduler", [
     (6, "credit2"),
     (7, "arinc653"),
     (8, "rtds"),
+    (9, "null"),
     ])
 
 # Consistent with SHUTDOWN_* in sched.h (apart from UNKNOWN)
-- 
<<This happens because I choose it to happen!>> (Raistlin Majere)
-----------------------------------------------------------------
Dario Faggioli, Ph.D, http://about.me/dario.faggioli
Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK)

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